/*
 * Copyright  2001-2002,2004-2005 The Apache Software Foundation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */

package net.sea.commons.util.zip;

import java.util.Hashtable;
import java.util.Vector;
import java.util.zip.ZipException;

/**
 * ZipExtraField related methods
 * 
 */
public class ExtraFieldUtils {

	/**
	 * Static registry of known extra fields.
	 * 
	 * @since 1.1
	 */
	private static Hashtable<Object, Class<?>> implementations;

	static {
		implementations = new Hashtable<Object, Class<?>>();
		register(AsiExtraField.class);
		register(JarMarker.class);
	}

	/**
	 * Register a ZipExtraField implementation.
	 * 
	 * <p>
	 * The given class must have a no-arg constructor and implement the
	 * {@link ZipExtraField ZipExtraField interface}.
	 * </p>
	 * 
	 * @since 1.1
	 */
	public static void register(Class<?> c) {
		try {
			ZipExtraField ze = (ZipExtraField) c.newInstance();
			implementations.put(ze.getHeaderId(), c);
		} catch (ClassCastException cc) {
			throw new RuntimeException(c + " doesn\'t implement ZipExtraField");
		} catch (InstantiationException ie) {
			throw new RuntimeException(c + " is not a concrete class");
		} catch (IllegalAccessException ie) {
			throw new RuntimeException(c
					+ "\'s no-arg constructor is not public");
		}
	}

	/**
	 * Create an instance of the approriate ExtraField, falls back to
	 * {@link UnrecognizedExtraField UnrecognizedExtraField}.
	 * 
	 * @since 1.1
	 */
	public static ZipExtraField createExtraField(ZipShort headerId)
			throws InstantiationException, IllegalAccessException {
		Class<?> c = (Class<?>) implementations.get(headerId);
		if (c != null) {
			return (ZipExtraField) c.newInstance();
		}
		UnrecognizedExtraField u = new UnrecognizedExtraField();
		u.setHeaderId(headerId);
		return u;
	}

	/**
	 * Split the array into ExtraFields and populate them with the give data.
	 * 
	 * @since 1.1
	 */
	public static ZipExtraField[] parse(byte[] data) throws ZipException {
		Vector<ZipExtraField> v = new Vector<ZipExtraField>();
		int start = 0;
		while (start <= data.length - 4) {
			ZipShort headerId = new ZipShort(data, start);
			int length = (new ZipShort(data, start + 2)).getValue();
			if (start + 4 + length > data.length) {
				throw new ZipException("data starting at " + start
						+ " is in unknown format");
			}
			try {
				ZipExtraField ze = createExtraField(headerId);
				ze.parseFromLocalFileData(data, start + 4, length);
				v.addElement(ze);
			} catch (InstantiationException ie) {
				throw new ZipException(ie.getMessage());
			} catch (IllegalAccessException iae) {
				throw new ZipException(iae.getMessage());
			}
			start += (length + 4);
		}
		if (start != data.length) { // array not exhausted
			throw new ZipException("data starting at " + start
					+ " is in unknown format");
		}

		ZipExtraField[] result = new ZipExtraField[v.size()];
		v.copyInto(result);
		return result;
	}

	/**
	 * Merges the local file data fields of the given ZipExtraFields.
	 * 
	 * @since 1.1
	 */
	public static byte[] mergeLocalFileDataData(ZipExtraField[] data) {
		int sum = 4 * data.length;
		for (int i = 0; i < data.length; i++) {
			sum += data[i].getLocalFileDataLength().getValue();
		}
		byte[] result = new byte[sum];
		int start = 0;
		for (int i = 0; i < data.length; i++) {
			System.arraycopy(data[i].getHeaderId().getBytes(), 0, result,
					start, 2);
			System.arraycopy(data[i].getLocalFileDataLength().getBytes(), 0,
					result, start + 2, 2);
			byte[] local = data[i].getLocalFileDataData();
			System.arraycopy(local, 0, result, start + 4, local.length);
			start += (local.length + 4);
		}
		return result;
	}

	/**
	 * Merges the central directory fields of the given ZipExtraFields.
	 * 
	 * @since 1.1
	 */
	public static byte[] mergeCentralDirectoryData(ZipExtraField[] data) {
		int sum = 4 * data.length;
		for (int i = 0; i < data.length; i++) {
			sum += data[i].getCentralDirectoryLength().getValue();
		}
		byte[] result = new byte[sum];
		int start = 0;
		for (int i = 0; i < data.length; i++) {
			System.arraycopy(data[i].getHeaderId().getBytes(), 0, result,
					start, 2);
			System.arraycopy(data[i].getCentralDirectoryLength().getBytes(), 0,
					result, start + 2, 2);
			byte[] local = data[i].getCentralDirectoryData();
			System.arraycopy(local, 0, result, start + 4, local.length);
			start += (local.length + 4);
		}
		return result;
	}
}
